Balancing system



P. D. ANDREWS BALANCING SYSTEM July 31, 1945.

Filed May 7, 1942 CIRCUIT j; ANTENNA 4Z4 Fig.4.

Pi g2.

Inventor Paul D. Andrews,

His Attorney.

Patented July 31, 1945 UNlTEl) STATES. PAT

cl rics 2.880.389 BALANCING srs'rm Paul D. Andrews, Schenectady, N. 1., assigns: to GeneraLElectric- Company, a corporation of- New York Application in, "7', 1942, semi Nor-442,046

v 3 (Cl. 178-44): My invention relates to radio or like circuits in- 1 corporating balanced push-pull devices, particularly to circuits in which a push-pull amplliler' or like device is coupled to a single-ended load It has been found that ii the single-ended. load circuit is resistive only, then although the neutralizing of the amplifier circuit is not affected, nevertheless the introduction of the resistive load has the serlolls'eflect of changing the relative amplitude and phase oithe radio ire-- quency output voltages oi the two amplifier tubes. the loading of the tubes thereby becoming unbalanced. Further. lithe load includes a reactive component still greater unbalancing is produced.

It has been necessary heretofore, in order to restore the push pull device to proper balance when pacitive compensating elements; Pig. 2 represents a 'modiflcation employing capacitive compensating elements: and Figs. 3 to 5 represent modifications employing inductive compensating elements. In Fig. 1 the numeral itdesignates a usual push-pull amplifier or like push-pull device comoutputcircuit to resonance.

prising a pair or electron discharge devices-ll f v and .II. The numeral 13 designates an output circuit which includes a capacitive means it constituted by capacitors or capacitor sections ii and it in series,and the numeral l1, an inductive means having windings II and it in series. Usual input circuit tuningv capacitors It and Ii and usual neutralizing capacitors 22 and '23 are provided.

The rectangle designates generally a singleended load circuit grounded at one extremity flii, and to which one extremity 28 or the output circuit 13 is connected. The load circuit 24 may be constituted by an antenna circuit or other like circuit, and may be resistive only or. may include a reactive component. The output circuit inductance i! may be made variable for tuning the The capacitors or capacitor sections it, it o! the capacitive means it in the output circuit are so arranged as to be made oppositely variable simultaneously as'incoupled to the single-ended load circuit, to efiect turning adjustments in one or more of the ca-- pacitive and inductive tuning elements in the output circuit of the device. Since'the tuned output circuit must be maintained at approximate resonance at the same time that'these adjustments are made. therefore such readjustments of the individual output circuit element to restore balance have been found to be very diillcult tomake and such method of restoring balanc to be impracticable in practice.

In accordance with the present-invention the foregoing dimculty is avoided by the provision of variable impedances in the output circuit 0! the push-pull device or impliller so'arranged eflect of the single-ended load circuit is accomplished without disturbing the total tuning of the output circuit for resonance. For this purpose the variable impedances may be constituted by capacitive or by inductive elements.

The novel features which are considered to be characteristic or my invention are set forthwith particularity in the appended claims. M invention itself. however, both-as to its organization 7 and method or operation together with further objects and advantages thcreot may best be understood by reference to the following description taken in connection with the accom-' panying drawing wherein Fig. 1 is a diagrammatic representation of a push-pull circuit arrangement incorporating my invention and including cathat balancing of each tube of the amplifier and in general the compensating for the unbalancing dicated by the oppositely extending arrows, for a purpose which will be explained presently.

In operation of the system illustrated sche matically in Fig. 1, to compensate for the unbalance in the loading or the discharge devices it and i2 tending to be produced because oithe coupling of the-push-pull device it to the singleended load circuit 24,. the capacitive means it is adjusted to increase or decrease as desired the reactance oi one of the capacitor sections, as, ll.

. while making a corresponding change in the opposite direction in the reactance of the other section, it. The design of the capacitive means It is such. however, that the reactance oi the capacitors or capacitor sections I5 and it in series remains substantially constant.

For a capacitance meansmeeting the abovementioned requirements for use, for example, in a high frequency push-pull system, a typical calibration may be as follows:

' Capacity of Capacity oi Rotor position in degrees sec. 16 in sec. 16 in v mmids. mmids.

6. 7 I). 0 10.0 10.0 20. 0 6. 7 so. 0 a 0 Assuming that the calibration oi the variable capacitive means is is substantially as above given for compensating for the load unbalance in discharge devices Ii and I2 occasioned by the and 3| respectively to be identical except that o the rotors are in opposed relation, the balancing the tuning of the output circuit 13 to resonance is not aflected by the varying of the capacitor, sections l3 and It for the purpose of compensating for load unbalance in the discharge devices.

In a practical case the constant capacitance thus provided by the capacitor sections l3 and It in series may be utilized as the total output circuit capacitance, any necessary tuning of the output circuit I3 to resonance being then accomplished by the inductance-means I! which may be made variable for this purpose.

Referring to Fig. 2, the system illustrated therein is in general the same as that illustrated in Fig. 1 except that Fig. 2 represents a case in which it is desired that the tuning to resonance oi. the-output circuit, 21, be efiected by means of a usual variable capacitance 28. In this case a capacitance means 29, corresponding to the capacitance means l4 Fig. 1. for compensating the unbalance caused by the single-ended load 24, is connected in shunt with the usual tuning capacitance 28, and is operated in the same manner as described in connection with Fig. 1.

Referring to Fig. 3, the system illustrated therein is similar in general to that of Figs. 1 and 2, differing therefrom in the means for compensating unbalance. In the system of Figs. 1 and 2 the unbalance of the push-pull stage is compensated by capacitive means. In some cases, however, the desired load balancing is more conveniently accomplished by variable inductance means such, for example, as provided by the two inductance elements 30 and 3| the reactance values of which are variedwhile the total reactance of these two elements in series in the output circuit remains constant. In the example shown in Fig. 3 the inductance means may be in the form of a variometer or similar rotating winding device having a stator constituted by stator windings 32 and 33, and a rotor constituted by rotor windings 34 and 35. One inductance element 30 of the above mentioned two inductance elements thus comprises a stator winding 32 and a rotor winding 34, and the other inductance element 3| comprises the other stator winding 33 and the other rotor winding 35.

In order that the reactanees of the two inductance elements 33 and 3| may vary oppositely for compensating the unbalance caused by the single-ended load 24, either the two rotor windings or the two stator windings are so wound or connected as to be in "bucking" or opposing relation. In the'present' case rotor windings 34 and 33 are illustrated asin opposing relation,

the stator windings 32 and 33 being in boosting" or aiding relation.

with the inductance elements 30 and 31 arranged as above described, thetotal' inductance of the rotor constituted by the two rotor windlugs 34 and 35 is equal to the sum of the inductances of each of the latter windings minus twice the mutual inductance between them. Also the total inductance of the stator constituted by the stator windings 32 and 33 is equal to the sum or their'inductances plus twice the mutual inductance between thelfi. Thus, assuming the winding arrangement 01 inductance elements 33 tance, 23.

means constituted by these inductance elements 30 and 3] provides a total reactance in the output circuit which is of constant value regardless of the position of the rotor. At the sametime when the rotors are moved to desired positions for compensating the unbalance caused by the" single-ended load circuit 24. the reactance of one rotor winding, as 34, in combination with a corresponding stator winding, as 32', varies inversely as the reactance of the other rotor winding 33 in combination with the other stator winding 33.

In the system above described in connection with Fig. 3, the rotor winding 34 in series or parallel with the stator winding 32 may constitute one section of the usual output circuit inductance, thus corresponding, for example, to

winding is of output circuit inductance l1 in Fig. 1, the other rotor winding 33 together with the other stator winding 33- constituting the other section of the usual output circuit inductance and corresponding to winding 13 'of inductance II. The inductance element 33 constituted by windings 32 and 34, and 3| constituted by windings 33 and 33 therefore may provide the total output circuit inductance means in cases where, as illustrated in Fig. 3, the normal output circuit tuning to resonance-is accomplished by means of a suitable variable capaci- Referring to Fig. 4, the system shown therein is similar to that of Fig. 3 except that in Fig. 4 the inductance means 33, 3| for compensating the load unbalance caused by the single-ended load 24 may be provided. if desired, in shunt with the usual output circuit inductance I1.

In Fig. 5, the variable inductance means for compensating the load unbalance is illustrated as being constituted by two separate but similarly arranged and connected variometers or rotating winding elements 33 and 31. To produce the desired compensating efiect the two devices are made oppositely variable as indicated by the oppositely extending arrows. Sincethe total output circuit inductance is the sum of the inductance of the various stator and rotor windings plus the sum of the mutual inductanceabetween corresponding sections of the stator and rotor windings, therefore the value of this total output circuit inductance remains constant-during the load balancing operation. 4

As in the system of Fig. 3. the load balancin elements 38 and 31 of Fig. 5 may constitute the entire inductance for the output circuit, as illustrated in Fig. 5, the tuning of the output cir-- cuit to resonance then being accomplished by a usual capacitive means 23, or, similarly to the system of Fig. 4, the load balancing elements 36 and 31 may be connected in shunt with a usual output circuit inductance.

My invention has been described herein in particular embodiments for purposes of illustration.

I within the true spirit and It is to be understoodjhowever, that the invention is susceptible of various changes and modifications and that by the appended claims I intend to cover any such modifications as fall scope 01 my inven-- comprising two electron discharge devices having cathodes connected together and anodes connected to opposite ends of said tuned circuit, said tuned circuit comprising two branches connected in parallel, one of said branches comprising two tunable reactance elements of one sign connected in series and having their center connection connected to said cathode and the other of said branches comprising a reactance element of the opposite sign whereby said circuit may be tuned to parallel resonance, said load circuit being connected between said center connection and one of said anodes whereby said push-pull device is unbalanced, and means for simultaneously varying oppositely the reactances, respectively, of said two elements while maintaining substantially constant the total reactance of said two elements in series whereby compensation for said unbalance of said device may be effected without disturbing the tuning of said tuned circuit.

2. In combination, a push-pull device and a tuned coupling circuit for connecting said device to a single ended load circuit tending to cause unbalance of said device, said push-pull device comprising two electron discharge devices having cathodes connected together and anodes connected to opposite ends of said tuned circuit, said tuned'circuit comprising two branches connected in parallel, one of said branches comprising two tunable capacitance elements connected in series and the other of said branches comprising an inductance element whereby said circuit may be tuned to parallel resonance, said load circuit being connected between said center connection and one of said anodes whereby said push-pull device is unbalanced, and means for simultaneously varying oppositely the capacitance, respectively, of said two capacitors while maintaining substantially constant the total capacitance of said capacitors in series whereby compensation for said unbalance of said device may be effected without disturbing the tuning of said tuned circu t.

3. In combination, a push-pull device and a tuned coupling circuit for connecting said device to a single ended load circuit tending to cause unbalance of said device, said push-pull device comprising two electron discharge devices having cathodes connected together and anodes connected to opposite ends of said tuned circuit, said tuned circuit comprising two branches connected in parallel, one of said branches comprising tunable capacitors and the other of said branches comprising two inductance elements in series and having their center connection connected to said cathode whereby said circuit may be'tuned to parallel resonance, one of said elements comprising a stator section and a rotor section in aidin ing relation, the other of said elements comprising a stator section and a rotor section in opposing relation, said load circuit being connected between said center connection and one of said anodes whereby said push-pull device is unbalanced, and means for varying the relative positions of said stators and their respective rotors thereby to vary oppositely the inductances, respectively, of said elements while maintaining substantially constant the total inductance of said tuning circuit to eflect compensation for unbalance without disturbing the tuning of said tuned 

